1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer-readable recording medium for determining a motion vector between a plurality of images.
2. Description of the Related Art
Conventionally, there have been disclosed techniques that calculate motion vectors between a plurality of frames to perform alignment between the frames.
A reference image refers to an arbitrary image frame in a motion picture frame. When calculating a motion vector of the reference image, a feature point that characterizes the image is used. Specifically, the calculation of a motion vector of the reference image is performed by calculating a difference between a feature point of the reference image and a certain region in a comparison image corresponding to the feature point. Japanese Patent Publication No. 3935500 discloses a method of dividing an image into triangular regions comprised of feature points when performing alignment between the frames by the motion vector of each feature point arranged irregularly. That is, by dividing an image into triangles having feature points at the vertexes, it is possible to estimate (interpolate) the motion vector of the pixel or region inside the triangle by the motion vectors of the feature points forming the triangle. Because of this, even when the feature points are arranged irregularly, it is made possible to calculate a motion vector with a certain kind of regularity.
However, the technique described in the above-mentioned Japanese Patent Publication No. 3935500 has such a problem that a triangle with an extremely large distortion appears depending on the arrangement of feature points. When interpolating a motion vector by a triangle with a large distortion, the following problems occur.
That is, because the distances between feature points constituting a divided region increase and the motion vector of a pixel and the like inside the region is estimated (interpolated) by the motion vector of the far distant feature point, there may be a case where the interpolation precision is reduced. In addition to the above, when the distortion itself of the region becomes too large, there is a possibility that the internal interpolation precision itself cannot be maintained any more.